Hazardous air pollutant and ozone precursor emissions from a low-NO x natural gas-fired industrial burner

Abstract

Due to heightened environmental concerns, urban areas throughout the world are switching to natural gas for fueling continuous stationary combustion systems. As natural gas systems shift to lean, premixed operation to reduce NO x formation and maintain high combustion efficiency, hazardous air pollutant and ozone precursor emissions—specifically, volatile organic compounds (VOCs)—may potentially increase. The regulation of stationary source VOC pollutants under the 1990 Clean Air Act Amendments may pose unforeseen challenges in the design and operation of advanced gas-fired combustion systems. The present paper investigates the relationship between VOC emissions and excess air, fuel-air mixing, and NO x and CO emission levels for a scaled, generic, low-NO x , natural gas-fired burner. The stack samples were analyzed for C 2 −C 10 aliphatic hydrocarbons, aromatic hydrocarbons, and aldehydes. Most VOCs were emitted in low concentrations (<100 ppbv). However, certain conditions or high swirl ability limits generated relatively high total VOC levels (≈.01–10 ppmC). The VOC concentrations correlated well with CO and total nonmethane hydrocarbon values, indicating that these two parameters may serve as surrogates for VOC emissions under lean conditions. The results suggest that there are selected optimal operating conditions that minimize all pollutants. If natural gas-fired systems operate at their optimal conditions, a significant regulatory concern with respect to hazardous air pollutant and ozone precursor emissions can be mitigated.